Investigation of the origin and distribution of heavy metals around Ebenezer Dam, Limpopo Province, South Africa

This study was based on the outcome of the soil geochemical survey which was conducted by the Council for Geoscience around Ebenezer Dam during 1995-1996, the results of which indicated high concentrations of lead (Pb), zinc (Zn) and arsenic (As). The current study therefore focused on the origin and distribution patterns of Pb, Zn, Cu, As and Cr withinthe environs of Ebenezer Dam and their potential impacts on the environment and human health. The work involved soil, sediment, rock and water sampling and analysis. Atomic absorption and x-ray fluorescence spectrometry were used to determine the metal concentrations. The occurrence of anomalous concentrations of these metals in the study area was established. The anomalies registered maximum concentrations of (mg/g): 57 for Pb, 157 for Zn, 313 for Cu, 73 for As and 888 for Cr. The concentrations of these metals in sediments along the streams were high near the anomalies, but decreaseddownstream. Concentrations of heavy metals in water around the Ebenezer Dam were found to be less than 0.01 mg/g ,except for As which was less than 1.0 mg/g. Thus Pb, Zn, Cu and Cr values were below the target water quality ranges for domestic, irrigation, livestock watering and aquatic ecosystem use. The study confirmed that the distribution of heavymetals in this area is localised within and around the source rocks that are felsic in nature, namely; granites and pegmatites that formed domes in the area

Use of compost bacteria to degrade cellulose from grass cuttings in biological removal of sulphate from acid mine drainage

The study focused on the use of compost bacteria to degrade cellulose from grass cuttings as energy and carbon sources for sulphate-reducing bacteria (SRB) in a biological reactor. The fermentation of grass cuttings was carried out by anaerobic bacteria isolated from compost, thereby producing volatile fatty acids (VFA) and other intermediates, which were used as carbon and energy sources for sulphate reduction by SRB. Grass was added daily to the reactor in order to obtain maximum production of chemical oxygen demand (COD) and VFA. The results indicated that daily addition of grass is essential for the efficient VFA production, sulphate reduction and for the cell growth of the microbial biomass. Sulphate reduction of 38% was achieved with an average reactor chemical oxygen demand/sulphate (COD/SO4) ratio of 0.56 mg/.. These results showed that 25 g of grass could produce enough VFA for a sulphate load of 25 g, which is a cost-effective method for sulphate removal

An investigation into the availability and role of oxygen gas in gold tailings dams of the Witwatersrand basin with reference to their acid mine drainage potential

The oxygen content of tailings dams around the Witwatersrand Basin was quantitatively measured over a period of 2 months using a multi-level gas sampling device (MLGS) in an attempt to understand the diffusion of oxygen in tailings dams as a result of acid mine drainage. The measured oxygen showed that the diffusion of oxygen in some Witwatersrand tailings dams is up to a depth of 4 m. In some instances the oxygen content in the layer 1m below the tailings surface decreased by a factor of more than 97% compared to the atmospheric content. The findings show that the development of oxidation zones in the tailings dams of Witwatersrand Basin which subsequently leads to acid mine drainage is limited by the amount of available oxygen in the tailings materials

Characterisation of gold tailings dams of the Witwatersrand Basin with reference to their acid mine drainage potential,Johannesburg, South Africa

Factors which play a role in acid mine drainage (AMD) formation were investigated over a period of 12 months. These include climatic, mineralogical, hydrological and oxygen diffusion parameters. The oxygen diffusion data reveal that the flow of oxygen in the Witwatersrand tailings dams is controlled by secondary porosity (i.e. cracks caused by roots on the dam surface). The age of the dam does not have a significant bearing on the extent to which the oxidised zone development and subsequently AMD can progress. Most of these processes take place within the first 3 m of the dams. The amount of rainfall plays a crucial role in determining the extent to which an oxidised zone progresses. The average oxidised zone in the 5 sites is 2.4 m ranging from 2.2 to 3.5 m. Water SA Vol.32 (4) 2006: pp.499-50